The application claims priority to a Taiwan application No. 096148945 filed Dec. 20, 2007.
1. Field of Invention
The invention relates to methods of growing nitride semiconductor material and more particularly to such a method of growing nitride semiconductor material with improved characteristics including increased flatness and decreased density of V-defects, thereby increasing yield and increasing light emission efficiency of LEDs (light-emitting diodes) made of a material including the nitride semiconductor material.
2. Description of Related Art
The rapid advances in light-emitting diodes (LEDs) have led to the advent of the solid-state lighting era for reduced consumption of natural resources. InGaN alloy is the most promising material for high-efficiency light sources because of its direct band gap nature and widely spanned emission spectrum from ultraviolet to infrared. Moreover, the excellent properties of GaN-based materials such as high temperature stability, high breakdown voltage, high electron velocity, strong piezoelectric effect and high current density let the GaN high electron mobility transistor (HEMTs), Schottky diodes, and hetero-junction bipolar transistors (HBTs) are a good candidate for the applications of high speed and high power.
However, the external quantum efficiencies (EQE) of InGaN green LEDs still falls short of what is required. Poor internal quantum efficiency has been identified to be the bottleneck and has become the focus of intensive studies recently. The fundamental issue of this task is to obtain high quality InxGa1-xN alloys at a high indium mole fraction, which often leads to low crystalline quality due to indium aggregation and/or phase separation. Furthermore, V-defects are the most common defect that occurs at InGaN/GaN quantum wells of high indium mole fraction. Previous works have demonstrated that the V-shape defects are easily formed in high indium MQW, not only from buffer layer treading dislocations, but also within the MQW because of strain relaxation associated with stacking faults or indium segregation. It is possible of increasing light emission efficiency of LEDs and increasing yield by increasing flatness and decreasing density of V-defects. Thus, it is desirable to provide a novel method of growing nitride semiconductor material.